1. Field of the Invention
This invention relates to a spheroidal graphite cast iron high in oxidation-resistance.
2. Description of the Prior Art
As conventional heat-resisting spheroidal graphite cast irons which require oxidation-resistance, there are high nickel content austenitic spheroidal graphite cast irons (niresist ductile iron) one example of which contains carbon (C), silicon (Si), manganese (Mn), chromium (Cr), nickel (Ni) and magnesium (Mg) in amounts of 1.78, 5.05, 0.55, 1.80, 35.8 and 0.079% by weight, respectively; the other example in amounts of 2.54 (C), 2.91 (Si), 1.05 (Mn), 3.03 (Cr), 20.0 (Ni), 0.016 (P), 0.011 (S) and 0.076 (Mg), respectively.
However, the former cast iron is expensive because of the high nickel content whereas the latter cast iron is inferior in oxidation-resistance and close adherance characteristics of oxide film (scale). Accordingly, conventional spheroidal graphite cast irons have been impossible to meet both the requirements of lower cost and excellent property.